Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$134.74	10.216%	$148.505	$148.51	$148.50	$148.50
Purchase #2	$120.36	6.554%	$128.2484	$128.25	$128.25	$128.20
Purchase #3	$175.30	8.830%	$190.779	$190.78	$190.80	$190.80
Purchase #4	$62.32	13.193%	$70.5419	$70.54	$70.55	$70.50
Purchase #5	$229.42	9.171%	$250.4601	$250.46	$250.45	$250.50
Purchase #6	$200.91	11.458%	$223.9303	$223.93	$223.95	$223.90
Purchase #7	$188.68	11.597%	$210.5612	$210.56	$210.55	$210.60
7 purchase totals =	$1,111.73		$1,223.0259	$1,223.03	$1,223.05	$1,223.00